This invention relates to waste treatment and more particularly to the removal of solid waste materials, having a high biochemical oxygen demand (BOD) and/or chemical oxygen demand (COD), from the liquid effluent of an industrial plant. These waste materials generally contain varying amounts of organic and inorganic by products from the particular processes being performed in the industrial plant and contain little or no sanitary waste materials. The invention includes a unique process utilizing the addition of chemical agents to effect sludge removal. It also includes a novel polyelectrolyte material for utilization in said process. It further includes means to carry out the process. The process and materials of this invention have been found to be particularly effective in removing wastes from the effluent of a cake baking plant.
In one type of industrial plant the waste material consists primarily of a single type of material, which can often be removed in a specific manner, as for example, that disclosed in U.S. Pat. No. 2,433,458, to Kahn et al, issued Dec. 30, 1947, for a method of treating pickle liquor used in the acid pickling of steel. In many other types of industrial plants the waste effluents contain varying amounts and forms of waste material. In such cases, it is often difficult to provide an efficient and economical process to remove these variable waste materials. The method of the invention is uniquely suitable to removing widely differing amounts and forms of waste material from the effluent of industrial plants. It has proven effective in treating bakery effluent, cesspool residue, restaurant wash water, commercial laundry water, water from used paper reclamation, and black liquor from a pulp mill.
Prior to this invention, it had not been possible to remove successfully, in particular, the wastes from the effluent of a cake baking plant, which effluent contains widely varying quantities of sugar, starch, flavorings, wash waters and various particulates.
While the method of the invention is primarily directed to the separating of waste materials from the water in the effluent of an industrial plant, it is also useful for the treatment of sanitary wastes. Generally it has been found to remove about 95% of the sanitary waste material from liquid sewage threby reducing the size of the subsequent biological treatment plant.
Problems have arisen when the waste material to be treated contains a very high biochemical oxygen demand (BOD) and/or very high chemical oxygen demand (COD). If this demand is not significantly lowered, the lagoons, lakes, rivers, etc., into which the effluent is eventually deposited, will become devoid of dissolved oxygen. This may produce septic conditions accompanied by foul odors, death of natural fauna, and a buildup of scum of the surface of the water.
It is not generally feasible to attempt to oxidize these materials since the expense of oxidizing agents would be very great. Hence, these materials must be removed from the effluent prior to discharge into the earth or into a body of surface water. The method of this invention is directed to removing a high percentage of oxidizable wastes from said waste liquor, thereby rendering the effluent sufficiently pure to be discharged into lagoons, rivers, lakes, municipal sewerage systems, or ground water.
Numerous treatment processes have been designed for removing industrial wastes, however, most of these have been unable to treat successfully waste liquors having a high concentration of dissolved solids and/or a large quantity of suspended solids without first greatly diluting the waste liquor with large quantities of fresh water. This not only increases the already strained demand for water, but necessitates use of a treatment plant of unduly large capacity.
Since the Environmental Protection Administration now limits the total quantity of solids, either dissolved or suspended, which may be discharged per day, a mere dilution technique is not permissible. The method of this invention eliminates these problems and provides for economical and efficient treatment of industrial waste liquors.
Prior to the process of this invention it has not been possible to successfully remove large quantities of dissolved and suspended matter from waste waters. Generally, efforts in this regard have been directed to the purification of drinking water, which involves the removal of quite small amounts of undesirable materials. See, for example, U.S. Pat. No. 677,668, to Koyl, issued July 2, 1901; U.S. Pat. No. 2,152,942, to Wilson, issued Apr. 4, 1939; U.S. Pat. No. 3,203,894, to Ikuno, issued Aug. 31, 1965.
While certain reactants utilized in the process of this invention have been utilized in prior water purification processes, as in the above-enumerated patents, and, for example, in U.S. Pat. No. 2,350,111, to Hood, issued May 30, 1944, U.S. Pat. No. 3,276,998, to Green, issued Oct. 4, 1966, U.S. Pat. No. 3,423,309, to Albertson, issued Jan. 21, 1969, and U.S. Pat. No. 3,846,293, to Campbell, issued Nov. 5, 1974, none of the prior processes have utilized these reactants in the manner of the invention which enables large quantities of waste material to be removed.
The apparatus of the invention includes at least one clarifier unit generally in the form of an open tank or reservoir in which unique baffle arrangements and a rotary impeller cause predetermined flow conditions for enhancing the forming of flocs and precipitates. Clarification apparatus in the form of a tank or reservoir with baffles and an impeller is shown in the Kahn et al patent, supra, and in U.S. Pat. No. 3,238,128, to Gustafson, issued Mar. 1, 1966. Other clarification apparatus in this form is sold by the Infilco Division of Westinghouse Electric Corporation in Richmond, Va. and is sold under the trademark "Accelator."